1. Field of Invention
This invention relates to printers for computers, and more particularly to compact, lightweight printers for use with portable computers.
2. Description of the Prior Art
The increased use of portable computers has created a need for compact, lightweight portable printers which can be conveniently carried by a computer operator. Two examples of prior art portable printers are the Diconix 150 and the Toshiba Expresswriter 301. Each of these printers is lightweight (approximately 4 lbs.) and each can print on a standard 8.5".times.11", letter size, or 8.5".times.14" sheet, legal size sheet of plain paper. However, although typically much smaller than standard desk-top printers, prior art portable printers continue to be undesirably large.
The undesirable size of the prior art portable printers accomodating 8.5" wide standard paper is mainly attributable to the cylindrical paper feed roller used to move a sheet of paper through the printer. The prior art paper feed roller is a solid, rubber-coated shaft approximately 11 to 12 inches in length. This paper feed roller is incorporated within the casing of the prior art portable printers. Therefore, the miniaturization of casings for prior art portable printers is limited by the paper feed roller to a length of approximately one foot.
It is therefore an objective of this invention to provide a portable printer case whose length during storage or transportation is substantially less than the length of the prior art portable or desk-top printers, but whose length while printing is capable of handling standard width-size sheets of paper. This objective requires that the length of the paper feed rollers within the printer case be adjustable between a shortened "storage/travel mode" and a full-length "operational mode".
One method of providing an adjustable paper feed roller is suggested in Tucker, U.S. Pat. No. 1,283,367. Tucker discloses a typewriting machine whose length can be expanded or contracted by the addition or subtraction of detachable sections of the paper feed roller, thereby accomodating different widths of paper. These detachable sections are screwed on or off of a main section of the paper feed roller. The adjustable paper feed roller is adapted to the typewriting machine by expanding or contracting an extensible carriage which reciprocates in front of a stationary typing head. The carriage is disposed to reciprocate outside of the main typewriting machine casing; therefore, the length of the adjustable paper feed roller is limited only by the adjustable parameters of the carriage.
The method for expanding a paper feed roller taught by Tucker is not easily incorporated into a modern portable printer case. First, the use of detachable sections of paper feed roller require the operator to carry the detachable sections with the printer and assemble the printer before each use. Moreover, because the assembled paper feed roller is solid, there is no reduction in cumulative weight from the portable printers discussed above. Finally, Tucker's expandable feed roller is incorporated into a manual typewriter and adjustments for incorporating the feed roller are limited to the reciprocating extensible carriage. Modern printers incorporate fixed paper feed rollers and a reciprocating printer head mounted on a carriage, all contained within a single case. Therefore, the use of Tucker's expandable feed roller would require redesigning the printer head carriage as well as the printer case to incorporate the stationary-head, reciprocating-roller features.